Copper threaded stack spacers. These spacers and useful for positioning components at an exact height in the stack.
Thread: M3 (3mm)
Outside Diameter: 5mm
Material: Copper
2mm – Weight: 0.21 grams each
3mm – Weight: 0.32 grams each
4mm – Weight: 0.43 grams each
5mm – Weight: 0.53 grams each

I like to use these threaded stack spacers as “StopLocks” in the stack. Because these spacers are threaded, when used with Loctite 243 they hold their position and prevent any force from the top nut being transmitted through to the Flight Controller dampeners.

As they also have a narrower diameter, these threaded spacers can be used in tight builds where clearance is limited.